RepositoryHookCommitCallback sometimes incorrectly returns commits that have not been added or removed to ref

Repository hooks that use PreRepositoryHook and/or PostRepositoryHook which were introduced in 5.0 that register a RepositoryHookCommitCallback can incorrectly get a onCommitAdded callback for commits that were neither added or removed, but are instead ancestors of the updated branch.

More specifically, this happens when for branches that are updated by merging in another branch.